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VERTEBRATE ANIMALS OF THE UXITED STATES 



Key to the Species of Onychomys 



ai Tail usually less than half the length of the head and trunk 0. leucogaster. 



a2 Tail usually more than half the length of the head and trunk. . . .0. torrid us. 



0. leucogaster (Weid) (Fig. 160). Body light mouse-brown above, 

 being darker middorsally, and snow-white beneath; a melanistic color 

 phase also occurs; length 150 mm.; tail 40 mm.; hind foot 20 mm.: 

 western America, from eastern Dakota and Kansas to eastern Califor- 

 nia; Mexico; 11 subspecies. 



Fig. 160. — Skull and tuberculate molars of Oyiychomys leucogaster {from Elliot). 



Subspecies of 0. leucogaster 



0. I. leucogaster (Wied). Size large; length 164 mm.; color dark: 

 eastern and central North Dakota into Manitoba. 



0. I. missouriensis (Audubon and Bachman). Size smaller; color 

 pale: western North Dakota and Montana and northwards. 



0. I. articeps (Rhoads). Like 0. I. fnlssourietisis, but still paler, 

 buff in color: Wyoming and South Dakota; southward to southwestern 

 Texas. 



O. I. brevicaudus Merriam. Size small; length 141 mm.; color 

 darker than 0. I. articeps: southern Idaho, northern Utah and Nevada. 



0. I. fuscogriseus Anthony. Color darker; size small: eastern and 

 central Washington, Oregon and northern California. 



0. I. melanophrys Merr. Color dark, being pinkish-cinnamon: 

 southern Utah and Colorado and northern New Mexico and Arizona. 



